Magnetic and Bathymetric Survey of the Suiyo Cross-Chain, Izu-Bonin Arc

Abstract

During the R/V Natsushima NT07-07 cruise, magnetic and bathymetric surveys of the Suiyo Cross-Chain were con- ducted. The newly collected bathymetric data fill gaps of swath coverage of previous cruises in shallow depths, therefore, a complete data set of swath bathymetry is obtained. The West Suiyo Volcanic Complex (WSVC) is magnetized in totality posi- tive, and has more complex distribution of the magnetization intensities and/or directions. The Suiyo Volcano (SV) is strongly magnetized. The magnetization intensities increase from the WSVC through the Suiyo Volcanic Ridge to the SV, i.e. from back-arc to volcanic front. It may indicate the SV mainly consists of younger basaltic rocks, while the WSVC consists of more differentiated rocks and/or is older. The western flank of SV is magnetized in positive, in contrast, the eastern flank may be magnetized in negative. Otherwise, the SV is interpreted as the magnetization of eastward declination. The deflection of the magnetic declination can be explained by the clockwise rotation of the seamount together with the Philippine Sea Plate. In the vicinity of the caldera of the SV has low or reverse magnetization. Low magnetization is likely due to hydrothermal activity in the caldera.